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This printer is using a so-called MK 10 extruder/hotend. These are a little different, there is a liner for the heat break that continues all the way down to inside the MK 10 nozzle: This PTFE tubular liner has an outer dimension of 4 mm and an inner diameter of 2 mm. The length of the tube is 34 mm. These tubes can be bought at pre-cut size or, more ...


2

What you are looking at is the top of a Makerbot MK10-style hotend. It appears that the filament has snapped off at the entry of the heat break at the top of the cold end. The image below shows how the hotend is constructed, from top to bottom, brasss nozzle, heater element block, heat break (with PTFE liner, or not if it is an all metal hotend) and the cold ...


1

This looks a lot like inadequate cooling as others suggested. A important aspect to consider is how long the printer spends on a single layer in the trubble areas and how big that area is. The faster a given layer the less time it has to cool. The smaller that area more time the hot nozzle spends in that vicinity heating the surrounding already printed ...


1

I have a Wanhao Duplicator i3 too. It does not matter a lot which ceramic wadding and / or kapton you use. The more you seal off, the better it works. If you have a full metal hotend and a powerful cooling blower and need temps above 250 °C, you might want to do the best you can with a good padding of ceramic and kapton. For normal operation, a half-done ...


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